A fuel cell system obtains electric energy by feeding combustion gas such as hydrogen and oxidation gas that has oxygen to a fuel cell and then electrochemically reacting them via an electrolyte. Air is employed as the oxidation gas fed to the fuel cell, and depending on places to be used, gaseous components (impurities) such as sulfur compound, nitrogen oxide, and the like are also contained. Having such impurities fed to the fuel cell may possibly deteriorate the fuel cell stack and cause decrease in generating efficiency.
As conventional fuel cell systems, there is a system that includes an impurity removing means for removing impurities contained in oxidation gas in the course of feeding the oxidation gas from an oxidation gas feeding device to a fuel cell, in order to prevent the impurities from flowing into the fuel cell (see Patent Documents 1, 2, 3, 4, and 5).
According to the fuel cell systems described above, it is possible to remove the impurities contained in the oxidation gas fed to the fuel cell, thereby preventing deterioration of the fuel cell stack. However, the impurity removing means has a limited capacity available for removal of impurities, and thus was required to be replaced or subjected to a regeneration process after being used for a certain amount.
In view of such a problem, a fuel cell system has been proposed as follows. An impurity removing means of this fuel cell system is capable of separating impurities removed from oxidation gas, and can output the impurities obtained by the impurity removal means from the system as occasion demands (see Patent Document 6, for example). This allows for regeneration and continuous use of the impurity removing means.    Patent Document 1: Published Japanese Translation of PCT Application No. 2004-508693    Patent Document 2: Japanese Unexamined Patent Publication No. 2005-116353    Patent Document 3: Japanese Unexamined Patent Publication No. 2004-327429    Patent Document 4: Japanese Unexamined Patent Publication No. 8-138703    Patent Document 5: Japanese Unexamined Patent Publication No. 2005-100967    Patent Document 6: Japanese Unexamined Patent Publication No. 2005-129494